A triglyceride composition is converted by enzyme interesterification of fat with fatty acid or lower alcohol ester thereof (hereinafter, referred to as “fatty acid ester etc.”) to increase purity of a specific triglyceride molecular species and thus to modify properties of the fat. However, this reaction is an equilibrium reaction, and therefore, when a target triglyceride purity is higher, a larger amount of an expensive raw material fatty acid ester etc. is required to be used, resulting in high cost.
In particular, high-purity USU fat and SUS fat (U: C18 unsaturated fatty acid, S: C4 to C24 saturated fatty acids) which are produced by interesterification with enzymes are highly demanded from the market, and inexpensive production process has been desired. However, use thereof in the market has not progressed due to high price due to the above reason.
As a fat rich in USU, for example, Patent Document 1 discloses a cocoa butter equivalent containing 40 to 100% by weight of mixed acid group triglyceride in which a saturated fatty acid with C16 to C22 is bound to a glycerin at 2-position and an unsaturated fatty acid with C16 to C18 and one unsaturated bond is bound to the glycerin at 1,3-positions as constituent fatty acids.
Patent Document 1 discloses that this mixed acid group triglyceride USU exhibits the following peculiar physical properties. The mixed acid group triglyceride USU forms a peculiar crystalline structure with mixed acid group triglyceride SUS, which is the main component of a cocoa butter. By combining the mixed acid group triglyceride USU as a raw material of a chocolate, a bloom is not observed at all without performing a tempering. The obtained chocolate shows that resistivity of a crystal against a pressure is significantly small although it shows a melting point almost same as that of ordinary chocolates.
As an example of a process for producing OStO (where St is stearic acid and O is oleic acid), which is one kind of the mixed acid group triglyceride, Example 1 of Patent Document 2 discloses a method including interesterification of fully hydrogenated soybean oil and ethyl oleate using 1,3-position-selective enzyme, molecular distillation, fractionation, and refining. However, ethyl oleate used for the production of OStO fat is relatively expensive, and there is a problem that if a high purity product is to be obtained, the production cost is high.
As a fat rich in SUS, for example, Patent Documents 3 to 5 disclose that powder particles mainly composed of BOB (B is behenic acid and O is oleic acid) are added to a chocolate compound without being dissolved, so that occurrence of a bloom is significantly suppressed, and in addition, tempering operation can be omitted. Thus, the fat rich in SUS is peculiar and useful fat material for the chocolate industry. However, behenic acid used for the production of BOB fat is still relatively expensive and has a problem of high production cost as described above.
As a fat rich in USU, for example, Patent Document 6 discloses a technique of using fat rich in OPO as a milk fat substitute composition, and Patent Documents 7 and 8 propose a process for producing a fat rich in OPO. However, there is no description concerning the collection and use of relatively expensive oleic acid used as a raw material, and it could not be said to be an efficient OPO fat production process.
Patent Document 9 discloses a production process in which a fat by-produced in the production of StOSt fat is hydrolyzed and then the resulting product is used for a fatty acid raw material for OPO fat production. However, there is no disclosure concerning effective utilization of components by-produced in the production of the OPO, and it could not be said to be an efficient OPO fat production process.